The present invention relates to fracturing operations and, more particularly to, methods of hindering the settling of proppant aggregates once placed into a fracture.
Various methods are known for fracturing a subterranean formation to enhance the production of fluids. In a hydraulic fracturing operation, a pressurized fracturing fluid can be used to hydraulically create and propagate a fracture within the subterranean formation. Fracturing fluids can also carry and deposit solids such as proppants into the fracture. Inside the fracture, the proppants can form a tightly packed permeable mass (sometimes referred to as a “proppant pack”). The proppant pack serves as a physical barrier that prevents the fracture from fully closing and as a conduit through which production fluids can flow. The degree of success of a fracturing operation depends, at least in part, upon the fracture conductivity once the fracturing operation is stopped and production is begun. The conductivity of these proppant packs are somewhat limited because of the relatively small interconnected interstitial spaces between the packed proppant.
Another fracturing approach involves placing a much reduced volume of proppants in a fracture in order to create a high porosity fracture. In such operations, the proppant particulates within the fracture may be widely spaced but still sufficient to hold the fracture open and allow for production fluids to flow. Increased fracture conductivity may result due to the fact that the produced fluids may flow around widely spaced proppant rather than through the relatively small interstitial spaces in a proppant pack. While this fracturing concept has been investigated in the industry, its widespread usefulness is still somewhat limited for a number of reasons. Among other things, settling of proppant can be particularly problematic when reduced volumes of proppants. Proppant settling may lead to a fracture or a top portion of a fracture closing, which can lower the conductivity of the propped fracture and result in proppant aggregation, rather than discrete proppant pillars. Proppant settling may be particularly problematic in cases where proppant aggregates are used in place of traditional proppant because the proppant aggregates tend to be larger and may be heavier and thus are more difficult to hold suspended. While settling may be counteracted by using a high pump rate or by increasing the viscosity of the fluid carrying the proppant or aggregates, such methods often lose effectiveness once the fluid is placed into a fracture and before the fracture pressure is released.